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Explain whether water is a polar molecule or not and explain why (3)
- O is more electronegative than H
- H₂O has a non-symmetrical shape
- This means the dipoles cannot cancel out, and so water is polar
What does it mean when a bond is non-polar? (1)
The electrons in the bond are evenly distributed
What are the three main types of chemical bonds? (3)
- Ionic
- Covalent
- Metallic
Define Ionic bonding (1)
The strong electrostatic force of attraction between oppositely charged ions
Give an example of an ionically bonded substance (1)
NaCl
Define covalent bonding (1)
The strong electrostatic force of attraction between a shared pair of electrons
Define metallic bonding (1)
The strong electrostatic force of attraction between a sea of delocalised electrons and positive metal ions
Electrons in which shell are represented in a dot and cross diagram? (1)
Outer Shell
Why do giant ionic lattices conduct electricity when liquid but not when solid? (2)
- When liquid the ions are able to freely move and so are able to carry charge -
- But when solid the ions are fixed in position meaning they cannot carry charge and hence are unable to conduct electricity
Giant ionic lattices have high or low melting and boiling points? Explain your answer (2)
- High
- Lots of energy needed to overcome the strong electrostatic forces of attraction between the oppositely charged ions
In what type of solvents do ionic lattices dissolve? and give an example (2)
- Polar Solvents
- Water
Why are ionic compounds soluble in water? (1)
The ions interact with the water molecules allowing them to dissolve
Draw a dot and cross diagram for NaCl (1)
Draw a dot and cross diagram for calcium chloride (1)
Draw a dot and cross diagram for a hydroxide ion (1)
Draw a dot and cross diagram for NH4+ ion (1)
What is it called when atoms are bonded by a single pair of shared electrons (1)
Single bond
What is a lone pair? (1)
A pair of electrons not involved in the bonding
What is a bonding pair? (1)
A pair of electrons involved in the bonding
What is a dative covalent bond? (1)
The strong electrostatic force of attraction between a shared pair of electrons where the shared pair comes from one atom
What does expansion of the octect mean? (1)
There are more than 8 electrons in the outer shell
What does electron deficient mean? (1)
The outer shell has less than 8 electrons
What are the types of covalent structure? (2)
- Giant covalent lattice
- Simple covalent lattice
Describe the bonding in simple molecular structures (2)
- Strong covalent bonds within the molecule
- Weak intermolecular forces between the molecules
Why do simple covalent structures have low melting and boiling points? (1)
Little amount of energy needed to overcome intermolecular forces that occur between the molecules
Can simple molecular structures conduct electricity and explain why it can or cannot? (2)
- Cannot conduct electricity
- No charged particles to carry charge
Simple molecular structures dissolve in what type of solvent? (1)
Non-polar solvents
What is the shape and bond angle in a shape with 2 bonded pair and 0 lone pairs? (2)
- Linear
- 180 degrees
What is the shape and bond angle in a shape with 3 bonded pairs and 0 lone pairs? (2)
- Trigonal planar
- 120 degrees
What is the shape and bond angle in a shape with 4 bonded pairs and 0 lone pairs? (2)
- Tetrahedral
- 109.5 degrees
What is the shape and bond angle in a shape with 5 bonded pairs and 0 lone pairs? (2)
- Trigonal Bipydramidal
- 90 degrees and 120 degrees
What is the shape and bond angle in a shape with 6 bonded pairs and 0 lone pairs? (2)
- Octahedral
- 90 degrees
What is the shape and bond angle in a shape with 3 bonded pairs and 1 lone pair? (2)
- Trigonal pyramidal
- 107 degrees
What is the shape and bond angle in a shape with 2 bonded pair and 2 lone pairs? (2)
- Non-linear
- 104.5 degrees
What is the bond angle of water (1)
104.5 degrees
By how many degrees does each lone pair reduce the bond angle? (1)
2.5 degrees
Define Electronegativity (1)
The ability for an atom to attract a pair of bonding electrons from a covalent bond
In which direction of the periodic table does electronegativity increase? (1)
Towards top right
What is the most electronegative element? (1)
Fluorine
How is a polar bond formed? (1)
When the two bonding atoms have differing electro-negativities
Why is H20 polar whereas CO2 is non-polar (6)
H2O:
- O is more electronegative than H
- H2O has a non-symmetrical shape
- This means the dipoles are unable to cancel out and so H2O is polar
CO2:
- O is more electronegative than C
- CO2 has a symmetrical shape
- This means the dipoles can cancel out and so CO2 is non polar
Draw a 3D diagram of CCl4 (1)
Non-polar
Draw a 3D diagram of CH2Cl2 (1)
What are the 3 types of intermolecular forces? (3)
- Hydrogen bonding
- Permanent dipole dipole forces
- Induced dipole dipole forces
What is meant by intermolecular force? (1)
Force that acts between molecules
In which type of molecule do we refer to intermolecular forces? (1)
Simple molecules
What is the strongest type of intermolecular force? (1)
Hydrogen bonding
Describe where permanent dipole dipole forces occur? (1)
Between polar molecules
Describe where Hydrogen bonding occurs? (1)
- Between polar molecules
- Containing N, O or F bonded to H
Describe where induced dipole dipole forces occur? (1)
Between non-polar molecules
Describe how London Forces(Induced dipole dipole forces) arise? (4)
- Electrons are randomly constantly moving meaning they are unevenly distributed
- This leads to an instantaneous dipole -
- This induces other dipoles of other molecules
- Induced dipoles attract one another
Are induced dipole dipole forces greater in smaller or larger molecules?
Explain why (2)
- Larger
- There are more electrons
CCl₄ has a higher boiling point than CH₂Cl₂. Explain why (4)
- CH₂Cl₂ is polar, so permanent dipole-dipole forces occur between the molecules.
- However, CCl₄ is non-polar, meaning only induced dipole-dipole forces occur between the molecules.
- Despite this, CCl₄ has a higher boiling point than CH₂Cl₂.
- The boiling point of CCl₄ is higher because it has more electrons, making it a larger molecule, and so its induced dipole-dipole forces are greater.
Does boiling point increase or decrease down the noble gases? Explain why (3)
- Increases
- Number of electrons increases down the group
Meaning the induced dipole dipole forces occuring between the molecules become greater
"Draw a diagram of Hydrogen Bonding (1)
Name 2 anomalous properties of water (2)
- Ice is less dense than water
- Water has a relatively high melting and boiling point
Why is ice less dense than water (1)
Ice has an open lattice structure
Why does water have a relatively high meling and boiling point? (1)
Lots of energy needed to overcome hydrogen bonds
State the properties of ionic compounds (3)
- Can only conduct electricity when molten or aqueous
- High melting and boiling points
- Soluble in water
When an acid is added to water what ion is released into the solution? (1)
H+
Define acid (1)
Proton donor
Describe the dissociation of a strong acid (1)
Fully dissociates
Define base (1)
Proton acceptor
What are amphoteric substances? (1)
Substances that can acts as both bases and acids
What is a shell? (1)
A group of orbitals with the same principal quantum number
What is the formula to determine how many electrons are in each shell? (1)
2n^2
How many electrons can the 1st shell hold? (1)
2
How many electrons can the 2nd shell hold? (1)
8
How many electrons can the 3rd shell hold? (1)
18
How many electrons can the 4th shell hold? (1)
32
What is an orbital? (1)
A region of space near the nucleus that can hold up to two electrons with opposite spins
What are the 4 types of orbitals? (4)
- s
- p
- d
- f
What is the shape of an s-orbital? (1)
Spherical
What is the shape of a p-orbital? (1)
Dumbbell shape
How many orbitals are found in an s subshell? (1)
1
How many electrons can be held in an s subshell? (1)
2
How many orbitals does a p subshell have? (1)
3
How many electrons can be held in a p subshell? (1)
6
How many orbitals are present in a d subshell? (1)
5
How many electrons can be held in a d subshell? (1)
10
How many orbitals are found in a f subshell? (1)
7
How many electrons can fill an f subshell? (1): - 14
14
What shape is used to represent the electrons? (1): - Arrow
Arrow
What letter is used to represent shell number? (1)
n
From which shell onwards is s orbital present? (1)
1st shell
From which shell onwards is p orbital present? (1)
2nd shell
From which shell onwards is d orbital present? (1)
3rd shell
What are the rules by which electrons are arranged in the shell (3)
- Every orbital in a subshell is occupied by a single electron before they pair up
- Orbitals with the lowest energy get filled first
- 4s is filled before 3d
Why does 4s orbital fill before 3d orbital? (1)
4s has a lower energy than 3d meaning it gets filled first
Which electrons are lost when an atom becomes a positive ion (1)
The highest energy electrons/ The outermost electrons/The electrons in the highest energy levels
What is meant by the term ionic lattice? (1)
A repeating pattern of oppositely charged ions
Define Allotrope (1)
A different form of the same element
Give 4 examples of allotropes (4)
- Diamond
-Graphite
- Graphene
- Silicon Dioxide
State some properties of diamond (3)
- High melting and boiling point
- Hard
- Poor conductor of electricity
What is the shape of diamond and bond angle? (2)
- Tetrahedral
- 109.5 degrees
Why is diamond hard? (1)
Its tetrahedral shape allows any force exerted on it to be spread across the lattice
What type of lattice does diamond or graphite have? (1)
Giant covalent lattice
State some properties of graphite (3)
- High melting and boiling point
- Soft
- Good conductor of electricity
What is the shape and bond angle of Graphite? (2)
Trigonal planar 120 degrees
Why is graphite soft? (1)
The layers in graphite are able to slide over each other
